sorry if this has been asked before, if it is, please help me finding the old post. I know how to properly adjust smallest and largest cassette position, however, in one or two middle gear, when switch over, it sometimes not get it and when I shift again, it switch two gears, something like that, also when I shift to lower gear ( smaller ring ), it sounds much larger when chain shift into the gear, sounds like it hopping with larger jump or something. Does anyone know if it sounds like the chain is too loose? or there is a place to adjust it? thanks!

Photos with the bike in the largest chainring ==> largest rear sprocket, and smallest chainring ==> smallest rear sprocket would help determine chain length.

Look at B-Screw adjustment. The idea is to adjust the jockey wheels as close to the rear sprockets without them actually touching. That should help with shifting a bit.

If the problem is worse going from a larger cog to a smaller cog, clean & lube the cable.

Also check the cable INSIDE the brifter for fraying. You will have to disconnect the cable from the RD and push it out an inch or
so from the brifter to do this. Older brifters can get wear in the ratchet mechanism that will do this as well. A thorough
washout and relube of the brifter could be considered.